1. Field of the Invention
The present invention relates to a control device. In particular, the invention relates to a gas flow control device.
2. Description of the Prior Art
In many chemical and physical processes, the flow of a fluid in particular a gas must be controlled and held constant over a given time. Often the requirement is to control or regulate the flow of a fluid, for example a gas, so that a constant mass of the fluid or gas per unit time flows to a user. Devices have been developed with a valve in a gas line regulated by measurement of the gas flow so that the gas flow has a desired value. Such devices require cable connections from the valve control unit, for example to a computer and back. In addition, the devices must be individually calibrated in a complicated way. A control accuracy of better than 1 percent is hardly achieved.